The present invention relates to a method for manufacturing a stator component that is intended in operation to guide a gas flow and to transfer loads.
The stator component can, for example, be utilized in a gas turbine and, in particular, in a jet engine.
By jet engine is meant various types of engine that take in air at a relatively low speed, heat it up by combustion and expel it at a much higher speed. The term jet engine includes, for example, turbo-jet engines and turbo-fan engines.
Such a stator component that comprises an outer and an inner ring with wall elements arranged between the rings, can be arranged with the aim of primarily being load-transferring in a radial and axial, and also in a tangential, direction. The wall elements can, for example, form hollow blades, which are usually such a shape that they present as little air resistance as possible. The component can, for example, be arranged in a rear or front support, or in an intermediate housing in a jet engine. In such cases, the blades are often called struts. Struts can, however, also be created by other types of part than hollow blades.
According to a previously-known technique, wall elements in the form of hollow blades are arranged spaced apart in the direction of the circumference of the component between an inner and an outer ring. The joining of the hollow blades to the rings is carried out by welding. Each of the rings is manufactured first with parts projecting in a radial direction that have the same cross-section and dimension as the blades.
Such projecting parts are often called stubs. Each of the blades is thereafter welded on to such a projecting part using a butt joint. The parts projecting in a radial direction are normally milled out of a ring.
This is a time-consuming and expensive operation.
According to another previously-known technique, the whole stator component is cast in a single stage. This requires, however, a large and very complicated casting facility.
It is desirable to achieve a method for manufacturing a stator component that provides a better weight-optimized component in relation to previously-known techniques, with the same or increased durability and life. In particular, however, a timesaving and more cost-effective manufacturing method is sought.
According to an aspect of the present invention, the component is constructed of at least two sections in the direction of its circumference, and the sectors are cast in separate pieces, positioned adjacent to each other and joined together by welding.
As the sectors are cast individually, there are certain advantages in relation to casting the whole stator component in a single step. One advantage is that in the event of a fault or a defect, it is not necessary to reject a whole stator component, but only one sector. An additional advantage is that the casting is less complex, with smaller parts of a less complicated design.
According to an aspect of the invention, the surface of each of the sectors that is intended to be welded is continuous. In other words, the welding surface has no interruptions or sudden changes in direction. By this means, it is possible to have an efficient welding process that provides a highly durable welded joint. In addition, the surface of each of the sectors that is intended to be welded is essentially of the same thickness in cross-section over the length of the whole surface. By this means, there is considerably less need to change the welding parameters during the welding process.
According to another aspect of the invention, other parts of the sector adjacent to the surface that is intended to be welded are set back slightly in the direction of the circumference relative to the welding surface in order not to interfere with the weld path. This applies, in particular, when the sectors are cast in such a shape that they each have at least one rib that extends in the direction of the circumference and projects in an axial direction. The sector is then cast in such a shape that the rib extends in such a way that there is a gap in the direction of the circumference between the end of the rib and the edge of the sector. This makes it possible to join the sectors together in a simple way after the sectors have been placed adjacent to each other. After the sectors have been placed adjacent to each other in the direction of the circumference, the sectors are thus joined by welding together the sectors' adjacent edges between the ends of the ribs in a radial direction.
According to a further aspect of the invention, after the welding together, the space between two adjacent rib edges is filled by deposition of material so that the ribs form a continuous structure in the direction of the circumference.